Apple Final Cut Pro 7 - Manual (Page 1240)

9 If you still see light fringing at this point, or if you were forced to use settings so extreme
in the Chroma Keyer that some of your foreground subject was eaten away around the
edges, apply the Matte Choker filter. After you apply the Matte Choker filter, adjust the
Matte Choker’s Edge Thin and Edge Feather sliders. This is the point where you should
work to eliminate all the background fringing.
Moving the Edge Thin slider to the right further shrinks the alpha channel around the
foreground subject, eliminating still more fringing. Moving the Edge Thin slider to the
left expands the alpha channel, allowing you to replace areas of the foreground subject
that were lost. The Edge Feather slider allows you to blur the edges even further, if
necessary.
10 If you’re satisfied with your key, but there is some color from the background that is
spilling onto the edges of your foreground subject, go back to the Chroma Keyer tab in
the Viewer and adjust the Enhance slider to desaturate this spill so that it’s not noticeable.
Don’t move the Enhance slider too far, or you may get undesirable coloration in the edge
of your subject.
11 If there’s still more colored spill on your foreground subject that the Enhance slider didn’t
eliminate, apply the Spill Suppressor filter.
The Spill Suppressor filter desaturates color spill that may appear anywhere on the
foreground subject, not just on the edges. For example, a little of the background color
may show through translucent areas of the foreground subject, such as wispy hair or
sheer clothing. Once you’ve applied the Spill Suppressor filter to your keyed clip, adjust
the Amount slider to determine how much to desaturate the spill color in the foreground
image.
12 To eliminate any unwanted elements that didn’t get keyed out, such as rigging and lights
around your subject or the edge of the blue or green screen itself, use the Crop parameter
controls in the Motion tab of the foreground clip to cut those elements out of the picture.
If the area you need to crop is irregular, you can apply a Garbage Matte filter, instead.
The image is cropped
on both sides to remove
extraneous elements.
1240 Chapter 72 Keying, Mattes, and Masks